Generally, an optical fiber used for an optical fiber communication system that is widely used has a structure in which the outer circumference of one core is surrounded by an outer cladding. As an optical signal propagates inside the core, information is transmitted. Recently, according to the wide use of optical fiber communication systems, the amount of transmitted information is rapidly increased.
In order to realize an increase in the transmission capacity of such an optical fiber communication system, it is known to transmit a plurality of signals using light propagating through each core by using a multi-core fiber in which the outer circumferences of a plurality of cores are surrounded by one outer cladding.
In addition, in order to realize an increase in the transmission capacity of the optical fiber communication system, a multi-mode communication has been known which performs information communication by superimposing information on light of an LP01 mode (basic mode) and superimposing information on light of each LP mode of a higher order than that of the basic mode such as an LP11 mode. In a case where such multi-mode communication is performed, a multi-mode optical fiber is used.
In Non Patent Literature 1 described below, a multi-mode multi-core fiber performing multi-mode communication using a multi-core fiber has been disclosed.
(Non Patent Literature 1) Y. Sasaki et al., “Large-effective-area uncoupled few-mode multi-core fiber”, Opt. Express, 20 (26), pp. B77-B84 (2012).